Immunohistochemistry: sole tool in diagnosing a rare case of primary vaginal amelanotic melanoma

Abstract

We report a rare case of vaginal amelanotic melanoma. Malignant melanomas are cutaneous and extracutaneous tumors that arise from embryological remnants of neural crest cells/melanocytes. Amelanotic melanomas at such rare locations can be misdiagnosed both clinically and radiologically. Therefore, histopathological examination and immunohistochemistry are mandatory for the diagnosis of these tumors. We diagnosed this case using histopathology and confirmed the diagnosis based on the presence of immunohistochemical markers human melanoma black 45 (HMB45) and S-100.

Keywords: Amelanotic melanoma; HMB45; Mucosal melanoma; Vagina.

Fig. 1. Hematoxylin and eosin stained sections show (A) a tumor in the subepithelium with junctional activity and surface ulceration. (B) Tumor cells arranged in cords with intervening thin fibrous septa. Cells are plasmacytoid with eccentrically-placed nuclei and abundant cytoplasm. (C) Numerous mitotic figures (arrow). (D) Tumor cells have prominent eosinophilic nuclei and few hyaline globules (arrow).

Fig. 2. Immunohistochemistry: (A) Tumor cell cytoplasm is positive for human melanoma black 45 (HMB45) and (B) nucleus and cytoplasm are positive for S-100